呼伦贝尔沙质草原风蚀坑积沙区的植被分带性

呼伦贝尔沙质草原现代风蚀坑主要包括平缓草地的简单风蚀坑、复合风蚀坑和固定沙丘的简单风蚀坑3种类型。坑后积沙区植被出现明显的分带性,且随风蚀坑及其下风侧积沙体的形态、尺度而发生变化。在平缓草地简单风蚀坑下风侧积沙体平面形态呈顺风向的舌状,由坑口至原生草地,随积沙厚度顺风向减小,依次出现沙蓬、冰草和百里香3个植被带;平缓草地复合风蚀坑后缘形成具有滑落面的大型流动沙丘,在沙丘背风侧顺风向依次出现舌状裸沙带、舌状拂子茅带及两侧的冰草带;固定沙丘风蚀坑坑后积沙呈裸沙形式穿越沙丘原有的山刺玫和小叶锦鸡儿两个灌木带,并在裸沙带外围形成舌状拂子茅带。风蚀坑下风侧积沙区植被的分带性反映了草地植被对风沙活动的响应,即随着坑后积沙体的扩大,草地植被由原生向沙生逆向演替。

Zonation of Vegetation on Depositional Area of Blowout in Hulun Buir Gassland

Three types of modem blowouts including simple blowout, compound blowout on level grassland and simple blowout on stabilized dune are identified in sandy grassland of Hulun Buir. We investigate the morphology and vegetation distribution of sand deposit of blowouts and the results indicate that the distribution of plant species has a characteristic of zonation and species vary with the morphology and scales of sand deposit. The projected configuration of sand deposit of individual blowout on level grassland is tongue-shaped. From the edge of blowout to primary grass- land there are three regular crescent-shaped plant zonations that were sequentially dominated by the species of Agriophyllum punger, ,Agropyron cristatum and Thymus mongolicu with sand transport direction. The depositional area of combined blowout are dismembered by the dune with slipface, bare tongue-shaped sandy zonation, crescent-shaped plant zonation of Calamagrostis epigejos following wind and stripped zonation dominated by Agropyron cristatum which are distributed in the two-sides of the two zonations on level grassland. On stabilized dune the bare depositional area of blowout that is tongued-shaped passes through the zonations of Rosa davurica and Caragana microphylla that grew on dune before the appearance of blowout and extends to primary The leeward of bare depositional area is occupied by crescent-shaped zonation of C, grassland. epigejos. Analyzing the factor of vegetation zonation,we found there is a cubic equation correlation between Shannon-Wiener index and burial depth of sand, which suggests that the depth of deposition may be the major factor in zonation. These results demonstrate that the vegetation zonation is induced by sand-wind activity on sandy grassland. of sand deposit of blowout, the primary grassland v verse succession.